Cosmic Background Explorer/DMR
Galactic or Ecliptic
COBE Quad Cube
There are six sky maps, corresponding to the two independent channels (designated A and B) and three frequencies (31.5, 53, and 90 GHz) of the COBE Differential Microwave Radiometers (DMR).
The maps are quadrilateralized spherical projections in either ecliptic or Galactic coordinates. A sparse matrix least squares minimization technique was used to derive, from highly redundant sky sampling, a differential temperature for each of 6144 map pixels while simultaneously allowing for instrumental and systematic effects.
The observations were made with a 7 degree beam and are presented in 2.8 degree pixels. The maps are in FITS files formatted as described in the DMR Explanatory Supplement.
File names indicate the frequency, channel, and world coordinates of the map (ecliptic by default; Galactic if specified). For example, the 53 GHz, channel A map in ecliptic coordinates is named dmr_skymap_53ghz_a.fits and its Galactic coordinate counterpart is named dmr_skymap_galactic_53a.fits.
Due to the differential nature of the observations, the maps
have unconstrained antenna temperature zero points. While
the dipole anisotropy has been removed to first order (see
note above), emission from the Galaxy remains. The DMR
Analyzed Science Data Sets include Galactic Emission Maps
and Cosmic Emission Maps. The latter result when the Galactic
emission is removed. The modeled Galactic components are synchrotron
emission (dmr_synch.fits), free-free emission (dmr_free.fits),
and thermal dust emission (dmr_dust.fits). Two techniques
were used to produce the Cosmic Emission Maps, a "subtraction
technique" in which the Galactic components are subtracted
from the DMR maps (dmr_dsmb.fits), and a "combination
technique" in which a linear combination of the DMR maps
is used to cancel the Galactic emission (dmr_dcmb.fits). Corresponding
to each of these maps is an equivalent map pixelized in Galactic
coordinates (e.g., dmr_dust_galactic.fits). For a more detailed
description of the Analyzed Science Data Sets and the corresponding
Galactic Coordinate Data Sets, see the DMR
Explanatory Supplement and references therein.